1. Field of the Invention
The invention relates to carboxy ethers, to methods for their manufacture, and to their uses.
2. Discussion of the Background
Carboxy ethers of formula (I) EQU [R--O(CH.sub.2 --CH.sub.2).sub.n --CH.sub.2 COO].sub.m M.sup.m+(I)
where R is a hydrophobic group, n is a number ordinarily between 1 and 100, and M is a hydrogen or an ammonium ion, or a monovalent or multivalent cation of valence m, have been known for a long time (U.S. Pat. No. 2,183,853). These carboxy ethers are used as surfactants in the areas of:
(i) washing and cleaning agents (Schulze, K., 1975, Seifen. Oele. Wachse. 101:37); PA0 (ii) petroleum recovery (Blazer, D. 1983, Oil Gas European Magazin. 1:50); and PA0 (iii) emulsification (as emulsifiers), in relation to metal treatment (Friedrich, W., and Riemer, H., 1988, Chemische Industrie. 4:49). PA0 R is PA0 x is 0 to 15; y is 1 to 40; z is 0 to 15; and PA0 M is an alkali- or alkaline earth metal cation, an ammonium cation, a C.sub.1-4 alkanolammonium cation, or a proton. PA0 (i) Alkxy compounds of saturated or unsaturated, straight chain or branched alcohols containing 6 to 20 carbon atoms; PA0 (ii) Alkoxy compounds of alkylphenols and alkylcyclohexanols in which the alkyl groups on the phenol or cyclohexanol are saturated or unsaturated, straight chain or branched and contain from 4 to 16 carbon atoms; PA0 (iii) Alkoxy compounds of dialkylphenols and dialkylcyclohexanols in which the alkyl groups on the phenol or cyclohexanol are saturated or unsaturated, straight chain or branched and have a total of 5 to 24 carbon atoms; and PA0 (iv) Alkoxy compounds of trialkylphenols and trialkylcyclohexanols in which the alkyl groups on the phenol or cyclohexanol are saturated or unsaturated, straight chain or branched and have a total of 7 to 28 carbon atoms.
These carboxy ethers can be produced by reacting the corresponding hydroxyethoxy compounds with chloroacetates or chloroacetic acid, in the presence of an alkali (Ger. Pat. 2,418,444), or by catalytic oxidation via oxygen (Ger. OS 28 16 127), hydrogen peroxide (Eur. OS 0 039 111), or butyl peroxide (Eur. OS 0 001 868), typically with palladium.
Aqueous solutions of these carboxy ethers have however only low viscosities. There is however a need for carboxy ethers which form high viscosity aqueous solutions.